A display medium employing a diffraction grating to define and represent a display pattern by the contour thereof, which enables the display pattern to move smoothly as the visual point moves and which allows the display pattern to move in various ways and is easy to produce. A display pattern ("DNP"),...http://www.google.com.au/patents/US5991078?utm_source=gb-gplus-sharePatent US5991078 - Display medium employing diffraction grating and method of producing diffraction grating assembly
